Many different types of arrows and arrow shafts are known for use in hunting and sport archery. Two arrow types of relatively recent design are the fiber reinforced polymer (FRP) arrows and the aluminum arrows wrapped with fiber reinforced polymer. FRP is a generic term including, but not limited to, fiberglass composites and carbon fiber composites. Aluminum arrow shafts covered with FRP are usually made of an aluminum core covered with carbon fiber and are often referred to as aluminum carbon composite (ACC) arrows, although any FRP may be used as the covering. Traditional FRP and ACC shafts have been produced by a number of different manufacturing processes. The first FRP arrow shafts were constructed with unidirectional reinforcing fibers aligned parallel to the axis of the shaft.
Prior designs and processes for constructing FRP shafts resulted in a low circumferential or hoop strength. The hoop strength of these arrow shafts was so low that the arrows could not withstand even small internal loads applied in a direction radially outward from the center of the shaft. For example, internal loads generated from inserting standard components into the inside of these types of shafts would likely have resulted in failure of the arrow shaft. Arrow components may include, but are not limited to, inserts, points, and nocks.
In an apparent attempt to address the limitations described above, modern FRP arrows with new types of construction have been developed. The typical modern FRP arrows include glass and/or carbon fibers arranged in multiple directions, as opposed to the unidirectional fiber arrangement of the earlier FRP arrows. The multi-directional fiber arrangement (e.g., fibers that run perpendicularly or at an angle relative to each other) increases the hoop strength of the shafts. This allows the shafts to support greater internal loads, including internal loads generated by insert components. Such modern FRP arrows have, however, been traditionally made having an outside diameter and wall thickness of a size sufficient to accommodate standard-sized inserts. These carbon-composite arrows were generally lighter than aluminum shafts, but were generally of the same spine. “Spine” is an industry-standard measurement of arrow shaft stiffness. An arrow must have certain spine characteristics, depending on its length and the draw weight of the archery bow, to achieve proper flight. Generally, the heavier the draw weight, the stiffer the spine (i.e., less deflection) must be. ACC shafts are also generally lighter than standard aluminum arrows of the same spine because they comprise a thin, light core covered with carbon composites.
As a major portion of the archery market has moved toward lighter weight shafts, the modern FRP and ACC arrow have gained widespread acceptance. Lighter arrow shafts have the principal advantage of higher velocities than a heavier arrow when launched from the same bow. Such higher velocities result in a flatter arrow trajectory. The practical advantage of flatter trajectory is that a misjudgment by an archer of the range to a target has less effect on the point of impact.
Nevertheless, FRP and ACC arrows have a number of significant drawbacks. For example, FRP and ACC arrows tend to weld to certain types of targets to some degree. Such “welding” results from the frictional heat generated by the carbon surface of the arrow when it passes into the target. The hot surface of the carbon arrow will soften the epoxy resin at the shaft and melt certain target materials, which will cool shortly thereafter. This makes FRP and ACC arrows difficult to pull from the target. The FRP and ACC arrows may also be damaged as a result of the forces required to remove them from targets. In addition, the FRP sometimes splits at the ends of conventional FRP and ACC arrows.